If Congress is unable to come up with a budget and reverse cuts in defense spending, the Air Force will have to slash flying hours again this fiscal year, Chief of Staff Gen. Mark Welsh warned on Wednesday.

Automatic spending cuts known as sequestration went into effect in March because Republicans and Democrats failed to agree on how to cut the deficit. The cuts could last for 10 years and cost the Defense Department $500 billion.

Meanwhile, Congress has been unable to agree on a budget for this fiscal year.The government is operating on a temporary spending measure known as a continuing resolution, which holds Defense Department spending to fiscal 2013 levels.

“If we continue with a continuing resolution and a sequester, we’ll probably cut about 15 percent of our flying hours,” Welsh told reporters. Readiness will continue to drop and in [fiscal year] ’15, if it [the cuts]continues, it will get worse.”

The Air Force had to stand down combat squadrons in fiscal 2013, causing readiness to plunge, Welsh said.

“Before sequestration, about 54, 55 percent of our combat units were what we consider fully mission-ready, combat-ready,” he said. “Sequestration has made that much worse. It’s put us in a position where we’re now in the high 30s, probably, I don’t know what the number is today, but that’s roughly where it’s been for the last few weeks.”

Ideally, the Air Force should have about 80 percent of its combat units ready to fulfill all of the service’s missions, but readiness has been declining for more than a decade.

Requalifying pilots who have been stood down costs between two and threetimes as much as maintaining readiness, but there is no money in the Air Force’s budget to spin squadrons back up, Welsh said.

The major commands are looking at how to mitigate the damage being done to readiness by staggering when squadrons are stood down, he said. One idea would be to have squadrons not fly for a period after they get back from deployments and then spin up as they get closer to their next rotation.

But standing down combat units does long-term damage to readiness, Welsh said.

“If you take a flying squadron that two or three months of every year stands down because we can’t afford to keep them flying at their normal rates, but then they fly fully up the other nine months, over time, those pilots in that squadron are not as good as those that fly every month,” he said.

The concept of having part of the Air Force ready for combat has been called “tiered readiness,” but Welsh said that term falls short of describing the scope of the problems.

“I would call it ‘not ready,’ ” he said. “We are going to have units that are not ready. It’s not a tiered readiness model. Tiered readiness is a model that you would use to have a ready force to do what you’ve been asked to do. We are not going to be ready to do all the things that we have a requirement to do.”

Having squadrons stand down for part of the year would mean the Air Force would be much less ready for an unplanned contingency, Welsh said.

“One of the benefits of air power is its responsiveness, its flexibility, its speed of movement,” he said. “If you’re not ready to do that then the nation is giving up options. We just want to make sure everybody understands that. Which options the nation wants to give up is really the nation’s business, not the Air Force’s business.”